I don't know what this GameVolt you're talking about is, I'm talking about GameJolt, with a J, which is a game distribution platform similar to itch.io, and GameJolt is also based in the US.
Also, GameJolt have their own rating system, called DGRS (not ESRB or PEGI, etc) (and only them uses it currently), which, for example, seperates Nudity and Sexual things, which means a game can have a rating saying there is non-sexual nudity.
I cant post images here, so i'd recommended you go to GameJolt, try creating a game (whatever name since you wont publish it), go the Maturity tab and look at what options they have for making the rating.

